How dual-bed cartridges with filter aid help streamline solid-phase extraction during sample preparation
Effective sample preparation is essential for accurate trace-level PFAS analysis in complex sample matrices, such as non-potable waters, solids, biosolids, and tissues. Solid phase extraction (SPE) is typically used, but good results are difficult to achieve if background PFAS are present or if sample components clog the SPE cartridges. EPA Method 1633, which has been validated in multiple laboratories, uses a wool-packed weak anion exchange (WAX) cartridge for matrix extraction, followed by a dispersive graphitised carbon black (dGCB) cleanup step, with many labs adopting a carbon cartridge instead of using dGCB. While effective, this two-cartridge approach with manually-packed wool adds extra time, complexity, and risk of introducing contaminants to the sample preparation process.
Resprep PFAS cartridges are a simpler solution
PFAS SPE sample preparation can be streamlined significantly with dual-bed Resprep PFAS cartridges, which combine SPE extraction and carbon cleanup into a single cartridge. In this fast, simple workflow, the ultra-clean WAX and CarboPrep Plus sorbents used in Resprep PFAS cartridges ensure that method performance requirements will be met. In addition, an optional, factory-packed filter aid eliminates the time and variability associated with manually packing glass wool. This ready-to-use solution prevents clogging so that even dirty matrices can be processed quickly with a single extraction.
Meeting performance requirements
Developed specifically to help labs meet PFAS performance requirements, dual-bed Resprep PFAS cartridges contain ultra-clean, high-quality WAX and carbon sorbent layers that provide effective extraction and cleanup. Every lot of Restek’s WAX sorbent is tested against Method 1633 PFAS analytes to demonstrate cleanliness and to ensure it does not contribute background PFAS. In addition, our high-performance CarboPrep Plus sorbent provides more effective and consistent cleanup than other carbon materials. The combination of both sorbents in a single cartridge makes sample preparation much faster and results in clean extracts and excellent analytical performance (view these results in Table 1 here).
Table I: Target recoveries (70-135%) were met for all PFAS in reagent water samples prepared using Resprep PFAS cartridges.
Factory-packed filter aid option ensures faster sample prep
Exclusive to Restek, Resprep PFAS cartridges are also available with a factory-packed filter aid that prevents clogs and keeps samples flowing better than manually packed glass wool. As shown in Table II, when technicians follow Method 1633 instructions to pack glass wool to half the height of the cartridge barrel for all sample matrices (Section 12.1.1), the amount of wool and packing density can vary significantly, which means sample flow and clogging can also be affected. The filter aid used in Resprep PFAS cartridges is uniform and provides effective, consistent filtering and protection. In an experiment comparing the flow of diluted ASTM wastewater matrix through Resprep PFAS cartridges with filter aid, WAX cartridges with manually packed wool, and WAX cartridges alone, only the Resprep PFAS cartridges with the factory-packed filter aid did not clog and were able to extract the full sample volume (Figure 1).
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